Within the scope of the manufacture of mattresses, cushions and other like elements one of the commonly used solutions is to structure their core from a spring carcass, provided with a number of springs that are duly stiffened to one another in order for the axes to be parallel and at right angles to the general mattress plane, to form a block shaped as a quadratic prism fitted with two side frames that each generally comprise a strip that is at all event rectangular, the frames being duly fixed to the block of springs, in particular fixed to all the marginal springs in such block, using wires or staples. Among the various existing possibilities, staples are convenient in that their ends cannot accidentally constitute sharp elements, and in particular butterfly staples are closed through flanges that determine tongue and groove couplings that will, if the staple should open slightly by chance, prevent the spring wire or the frame rod from being released, as is the case with rectangular staples.
The best solution is therefore currently where the springs fixed to the side frames in order to make up the carcass are so fitted by staples and in particular using butterfly staples.
This stapling operation is sometimes effected manually, either using pneumatic guns with prefabricated staples, where the operator moves to find the best places for the staples or with fixed unit stapling positions above which the operator places the spring carcass, moving the same as the staples are provided, which being fixed can also become means with a self-production of staples from a reel of material.
There are machines that in addition to having stapling heads are able to produce their own staples, their disadvantages being on the one hand that they work horizontally, viz. with the spring carcass resting on one of its face-sides, thereby taking up a considerable amount of space, which is frequently not available, and are in any event very expensive, a further aggravation being that the machine is structurally very complex, expensive and uses a considerable amount of stapling heads acting only on one of the faces of the spring carcass, whence the said carcass must be overturned once the springs on one of its faces have been stapled.
There are also machines that could be termed "vertical" inasmuch as they work with the spring carcass positioned vertically, thereby taking up a considerably smaller amount of space, but machines of this kind known to date are only able to use prefabricated staples, and are also structurally complex and not fully automated.